Network convergence is a process whereby a set of networking devices exchange network topology information to establish a synchronized view of the current network topology for the network and both compute and install the corresponding forwarding state. A routing protocol and or a set of discovery protocols are utilized by the set of networking devices to exchange topology information. The state of network convergence is achieved once all topology information has been distributed to all of the network devices in the network and the corresponding forwarding state installed.
A network convergence time is a measure of how fast the overall set of network elements in a given network is able to collectively reach the state of network convergence. When a topology change has occurred, such as the failure of a link or node, data traffic may be disrupted for the duration of the network convergence time that may result in loss or delay in packet forwarding or similar operations until a new state of network convergence is reached, therefore it is desirable to minimize convergence time.
Similarly, service convergence is a state of a set of networking devices that support services for which a component of the service is the exchange of data via multicast forwarding. Thus, each service can be associated with one or more multicast distribution trees that define the forwarding of multicast data traffic associated with a given service. When the network resource model changes, or the set of subscribing nodes for a service is altered, or the resource requirements of a service instance are changed, the service convergence state is lost and must be recalculated. The time for re-establishing the service convergence state is the service convergence time. During the re-establishing of the service convergence state data traffic for the impacted services may be disrupted. The overall time required to perform service convergence in the absence of any network topology changes may be relaxed as it is not necessarily service impacting, and the service convergence process can be performed in a more controlled fashion than network convergence.